How do tech. startups do scoping/requirements on projects?

I ask this considering my background as a developer and now more as a Technical Business Analyst/Project Manager. My work has always been with big corporate banking giants and the role of a BA/PM is very critical in dealing with huge development and QA teams. In a startup, obviously there is no need for such fat especially in the beginning. But I am wondering if this changes as you scale bigger and need to define these type of roles. Sometimes the line is thinner and lot of developers are doing analysis anyway. But just wondering. TL;DR: Do startups at some stage hire Business Analyst/Project Manager or these roles ?